The purpose of this proposal is to study mechanisms of normal cognition by examining the cognitive mechanisms of the split-brain human. These unique patients allow for the separate psychological testing of each cerebral hemisphere working in isolation from the cognitive influence of the other. As a result, one can identify particular cognitive strategies that are uniquely active in specific kinds of perceptual-motor tests. Secondly, the sometimes presence of a language substrate in the isolated and mute right hemisphere enables one to a) identify possible alternative speech processing strategies, and b) to examine the amount and kind of cognition that can occur in a limited language system. Lastly, a variety of visual-perceptual as well as cognitive-emotional issues can be examined because of the special disconnection aspects of the surgery.